Vascular diseases, such as atherosclerosis and the like, have become quite prevalent in the modern day. These diseases may manifest themselves in a number of ways, often requiring different forms or methods of treatment for curing the adverse effects of the diseases. For example, vascular diseases may take the form of deposits or growths in a patient's vasculature which may restrict, in the case of a partial occlusion, or, stop, in the case of a total occlusion, blood flow to a certain portion of the patient's body. This can be particularly serious if, for example, such an occlusion occurs in a portion of the vasculature that supplies vital organs with blood or other necessary fluids.
To treat these diseases, a number of different therapies have been developed. For example, treatment devices have been developed that remove the material occluding a vascular lumen. Such treatment devices, sometimes referred to as atherectomy devices or ablation assemblies, use a variety of material removal devices, such as rotating cutters or ablaters for example, to remove the occluding material. (The term "atherectomy device" as used in the specification refers to a device for removing an occlusion in any portion of a patient's vasculature. Thus, while the atherectomy devices provided in accordance with preferred embodiments of the present invention are well suited for use in the coronary arteries, their use is not limited to the coronary arteries.) The material removal device, such as a rotatable burr, is typically rotated via a driveshaft that extends out of the vasculature of the patient and to an electric motor or turbine which is typically powered by a fluid such as air.
In operation, a material removal device secured to the distal end of a driveshaft is typically advanced over a guide wire placed in vivo until the material removal device is positioned just proximal to the occluded site. A drive assembly having a motor or turbine is used to rotate the driveshaft and the material removal device while the material removal device is moved through the occluded vessel. The material removal device engages the occluding material and removes the material from the vessel, rather than merely displacing or reforming the material as in a balloon angioplasty procedure.
An example of a currently available ablation assembly is the Rotablator.RTM. atherectomy system, manufactured by Boston Scientific. In this system, a main advancer housing encloses the drive assembly and a guide wire brake. An ablation device, such as a burr, and a rotatable driveshaft, are coupled to the drive assembly in the advancer housing, such that torque from the drive assembly is transmitted to the driveshaft, and the burr is advanced and retracted via longitudinal motion of the drive assembly.
As discussed above, the ablation device is typically advanced over a guide wire. The guide wire extends longitudinally through the entire ablation assembly, including the guide wire brake, drive assembly, driveshaft and ablation device. In operation, once the guide wire and ablation device are positioned within the patient's vasculature at a desired location, it is desirable to clamp the guide wire with the guide wire brake to prevent any longitudinal or rotational movement of the guide wire, prior to activating the drive assembly.
In the guide wire brake assembly currently manufactured by Boston Scientific, a collet having a passageway extending therethrough is positioned between an air-actuated piston and a brake retainer. Prior to activating a turbine of the drive assembly, air is provided to the piston, causing it to move toward the retainer against an end of the collet. The pressure of the piston against the end of the collet causes the collet to close around the guide wire, thereby preventing longitudinal and rotational movement of the guide wire. Although such a conventional brake assembly provides acceptable results, it is relatively expensive to manufacture and it can be difficult to thread the guide wire through the brake. It would therefore be desirable to provide a guide wire brake for an ablation assembly that provides good control of the guide wire, while simplifying use and reducing manufacturing costs. The present invention fulfills these needs, and provides further related advantages.